There are numerous applications where there is a need of detecting a component or sensing a level of a component in bodily fluids. These may be e.g. to diagnose an illness, adjusting a medication or detecting undesired or illegal substances in the body of a person.
As one example, glucose monitoring is part of an everyday life, especially for people with diabetes. To accommodate normal life, diabetic individuals need to accurately and frequently measure the glucose level in the body, preferably in a small amount of bodily fluid. The most common method to determine the blood glucose level is to use disposable glucose test strips and a glucose meter, see U.S. Pat. No. 5,951,836. To extract blood, a lancet pricks the finger and a drop of blood is placed on the strip. The main drawback with the glucose test strips is the pain from the extraction of blood using the lancet as well as the skin damage.
Other methods to measure the glucose level have been suggested in the prior art. The main goal is to develop a non-invasive method (see “The Pursuit of Noninvasive Glucose: Hunting the Deceitful Turkey”, John L. Smith, Second edition 2011). Measurement techniques range from spectroscopic, optical, light scattering, breath and transdermal techniques. Techniques fail primarily due to difficulties to obtain an accurate glucose measurement. It has however been shown that the glucose level in interstitial fluid (ISF) correlates well to the blood glucose level (Suresh et al. “Comparison of glucose concentration in interstitial fluid, and capillary and venous blood during rapid changes in blood glucose levels”, Vol 3, No 3, 2001, Diabetes Technology and Therepeutics).
The use of microfabrication to reduce the size of needles to minimize discomfort is a rapidly developing arena of investigation for the transcutaneous delivery of drugs. Such microneedles have been developed for extracting ISF transdermal, see U.S. Pat. No. 7,753,888.